@Jan-Poo. The reason he gives his own phone is, that he is already convinced that Pantsu is already familiar with more than enough stuff to be able to decode something useful. However I agree it is a big risk to give him his own phone, he could have deceived him by giving him #4's and later on when Akira sees he is legit and probably will help him, show his own phone.
(I saw no reason why would he take #4's phone while he already has one functional. And I found it odd we haven't seen any sign of it for like ~5 episodes)
@Fish Eric.
I don't think Pantsu is a selecao though. He should be more active, and initiative than we were led to believe, in order to have a chance of winning the game. Additionally there would be no reason to be obsessed about the other selecaos if he is one. He could just check the transactions in his own phone if he is curious about them.
Although if he is indeed a selecao, I would probably bet money on him being #12. However the likelihood IMHO is low.